The markup is simple. Just a nav in which we place some links. Also we need some triggering for the responsive part, so I did add two toggles. One within the nav and one outsiet of it. And then I just used some icons for it. I used Font Awesome for that.

For the styles we use flexbox, so we only have to change one line and the menu items are underneath each other. in responsive mode we hide the menu with a transform. And once the active class is triggered, it will slide back in.